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Urban geochemistry in ,

ROLF TORE OTTESEN & MARIANNE LANGEDAL

Ottesen, R.T.& Langedal, M.2001: Urban geochemistry in Trondheim, Norway.Norges geologiske undersøkelse Bulletin 438, 63-69.

The chemical composition of urban surface soil in Trondheim, Norway, has been mapped to serve a two-fold pur- pose. 1) To assess whether stack-emissions from industrial sites, incinerators and crematoria, as well as road traffic, have caused local elevated concentrations of certain elements. 2) To provide a database for environmental health risk evaluation.Surface soil samples were collected from 314 sites in gardens,parks and industrial areas.The samples were analysed for the Aqua Regia soluble fraction of 31 elements. Natural background concentrations were deter- mined in the deeper parts of overbank sediment profiles from the region. In general, the pollution levels were low. However, Cd, Hg, Pb and Zn pollute the surface soils in the central and older parts of the city and along the main roads. The most dominant sources are presumably automobile exhaust (Pb), tyre wear (Zn and Cd), and emissions from a crematorium or a hospital incinerator (Hg). In the eastern parts of Trondheim, industries burning coal have probably caused elevated As concentrations.

Rolf Tore Ottesen1 & Marianne Langedal, Department of Environment, City of Trondheim, N-7004 Trondheim, Norway 1. Present address: Geological Survey of Norway, N-7491 Trondheim,Norway. E-mail: [email protected] & [email protected]

Introduction traffic had caused local, traceable pollution. 2) To provide a Urban environments are polluted by a number of different database for environmental health risk evaluation. In addi- sources such as road traffic, industry, waste incineration, tion, the dataset should provide background knowledge for waste sites,crematoria and incineration of coal,oil and wood further community planning. In this article we present a (e.g., Berglund et al.1994, Birke & Rauch 1994, Ahlgren 1996, brief overview of the methods used and the main results of Chen et al. 1997, Mielke & Reagan 1998, Mielke et al. 1999, the mapping. and Ottesen et al. 2000a & b). Spills and deliberate disposal from point sources have caused extremely high levels of pol- Study area lutants in soils at industrial sites and waste dumps (Ottesen Geography et al. 1989, Karlsaune 1995). Airborne pollutants are The city of Trondheim lies in central Norway, 350 km south deposited on surface soils and often accumulated in the soil of the Arctic Circle (Fig.1). The climate is typically cool and compartment. Lately, it has been observed that general con- humid. Trondheim was founded in 997, and during the first sumption and waste disposal have caused non-point pollu- 900 years of its history the was concentrated in tion of urban soils (Ottesen et al. 2000a, Langedal & Ottesen the present city centre (Fig. 2). During the the 20th century, 2001). Soils act as reservoirs for heavy metals and organic the urban area increased markedly and today the densely micro-pollutants. Human activity may create pathways from populated area covers 70 km2.The city now has a population these reservoirs to the urban populations. Thus, the quality of 164, 000. of urban soils can influence human health (Mielke & Reagan 1998). Geology Only a few urban soil studies have so far been carried Metamorphosed volcanic and sedimentary rock sequences out, compared with the number of studies on agricultural of mainly Early Ordovician to Early Silurian age constitute a and forest soils. A survey of the content of inorganic and significant part of the allochthon in the Caledonides of cen- organic pollutants in urban soil can serve as a basis for com- tral Norway (Wolff 1979). The Støren Nappe of the Upper munity planning and to assess the need for emission regula- Allochthon dominates in the (Gale & tion. Roberts 1974, Roberts & Gee 1985). The main rocks in and In Trondheim, the third largest city in Norway, concern around the city are MORB-type tholeiitic basalt with subor- about local air pollution was expressed in the early 1990s, dinate cherts and hemi-pelagic sedimentary rocks and also and in 1994 the city administration decided to map the bodies and dykes of trondhjemite, all metamorphosed at chemical composition of urban surface soils in order to eval- greenschist facies.These form part of the ophiolite uate the state of pollution.This geochemical mapping had a (Slagstad 1998). two-fold purpose:1) To assess whether stack-emissions from Most of the city is situated on marine clay, deposited industrial sites, incinerators and crematoria as well as road about 10, 000 years ago as the sea-level rose during 60363_NGUBull438_INNMAT 21.04.05 12:57 Side 64

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Fig. 2. Map showing the development of densely populated areas in Trondheim during the period 1909-1987.

the populated parts of Trondheim, 314 samples were col- lected at a density of 4.5 samples per km2 (Fig.1). The sam- ples were collected from areas consisting of marine clay, flu- vial sediments or reworked urban soil. From each site, grass was removed before one half kilogram of material was col- lected at 0-2 cm depth. The samples were packed in paper bags and air dried. Overbank sediments of varying age from the river and from 55 other rivers or streams in the area were also sampled and analysed to study the chemical changes through time (Hana 1996, Ottesen et al. 1989, 2000c). The element concentrations in the deeper and older overbank sediments were interpreted as providing a reasonable indi- cation of pre-industrial, natural concentrations.

Fig. 1.The study area smapling points for surface soils (314 samples) Chemical analysis, inorganic substances The samples were sieved through a 2-mm nylon cloth. One deglaciation.Later,isostatic forces caused a relative sea-level gram of this < 2 mm sample material was digested in hot

decrease leaving the marine clay onshore. Along the Aqua Regia ( 3ml 3:2:1 HCl:HNO3:H2O). The solutions were Nidelva river, the city rests on fluvial sediments (Reite 1983, analysed for 31 elements by ICP-AES. In addition, the solu- Reite et al. 1999). In the city centre, the overburden has been tions were analysed by GFAAS for As and Cd. Hg was deter-

used and recycled many times during historical times. It is mined by AAS (cold vapour technique) after HNO3 diges- therefore difficult to determine the original type of material tion. Se was determined after HNO3 and H2O2 digestion.The (Reite et al. 1999). analytical work was carried out by the Geological Survey of The urban soil also contains building materials (bricks, , which is accredited after EN 45001. paint, concrete, metal), waste, ash, slag, transported soils, organic materials and local original mineral matter (Ottesen Loss-on-ignition et al. 1999a & b, Langedal & Ottesen 2001). Loss-on-ignition was determined in all samples by heating 2 grams of material of each sample to 200°C for 2 hours, fol- Methods lowed by 20 hours at 430°C. Sampling and sample preparation Surface soil was selected as the sampling medium since it is Statistical methods readily accessible and is known to accumulate airborne pol- The analytical results were treated statistically by summary lutants.From gardens,parks,fields and industrial sites within statistics and factor analysis. 60363_NGUBull438_INNMAT 21.04.05 12:57 Side 65

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Table 1. Contents of aqua regia extractable elements in 314 samples of surface soil from Trondheim, Norway. Mineralogical analysis Twelve samples of surface soil (6 samples of marine clay and Element Arithmetric Median Minimum Maximum mean 6 samples of fluvial sediments) were analysed by XRD for Al (%) 1.91 1.86 0.17 4.47 determination of the main minerals present in the samples. As (mg/kg) 3.0 2.8 0.5 83 B (mg/kg) 5.8 5.0 3.0 28.0 Ba (mg/kg) 77.4 72.2 18.0 385 Results and discussion Ca (%) 0.68 0.54 0.06 10.60 Geochemistry of surface soil from Trondheim Cd (mg/kg) 0.24 0.16 <0.01 11.3 Table 1 summarizes the results of the chemical analyses.The Co (mg/kg) 14.4 13.5 1.6 45.0 geographical distributions of high and low concentrations Cr (mg/kg) 73.3 69.3 7.9 199 vary from one element to another (Fig. 3). Comparison with Cu (mg/kg) 42.3 34.5 1.7 706 Fe (%) 3.21 3.10 0.33 8.49 the regional and local geochemical background (Table 2) Hg (mg/kg) 0.21 0.13 0.02 4.49 shows that Pb, Zn, Ba and Mg are significantly enriched in K (%) 0.29 0.23 0.04 1.11 the urban surface soils.The enrichment of Cr, Cu, Fe, Ni and V La (mg/kg) 15.9 15.4 1.4 33.8 in the same material is less significant. Li (mg/kg) 18.5 17.8 0.9 39.3 Mg (%) 1.34 1.29 0.15 3.04 Mn (mg/kg) 479 442 43 4410 Table 3 Principal component factor analysis of the correlation matrix. Mo (mg/kg) - - <1.0 7.2 Rotated factor loading and communalities. (Varimax rotation). Na (%) 0.02 0.02 0.007 0.76 Ni (mg/kg) 47.8 45.0 6.0 231 P (mg/kg) 848 794 50 2480 Variable Factor 1 Factor 2 Factor 3 Factor 4 Factor 5 Communality Pb (mg/kg) 51.2 35 9.0 976 LogCo 0.964 0.080 0.033 0.035 -0.179 0.970 S (mg/kg) 605 475 37 4813 LogCr 0.950 0.040 0.063 0.036 -0.086 0.934 Sc (mg/kg) 3.6 3.3 0.1 9.2 Logv 0.935 0.205 0.037 0.183 0.058 0.953 Se (mg/kg) 0.27 0.20 0.04 3.69 LogFe 0.910 0.371 0.040 0.071 0.008 0.973 Sr (mg/kg) 30.8 27.0 5.8 255 LogNi 0.901 0.183 -0.026 -0.087 -0.262 0.922 Ti (mg/kg) 1171 1110 83.8 3170 LogMg 0.901 0.308 -0.012 -0.039 -0.197 0.947 V (mg/kg) 55.6 55.1 6.7 144 LogMn 0.853 0.061 0.102 0.107 -0.092 0.761 Y (mg/kg) 8.4 8.0 0.6 17.5 LogTi 0.824 0.246 -0.176 -0.164 0.003 0.801 LOI (%) 13.7 10.9 0.4 91.5 LogAl 0.822 0.521 -0.036 0.123 0.093 0.972 La 0.099 0.941 -0.120 0.083 -0.033 0.917 Y 0.230 0.882 -0.150 -0.175 -0.153 0.907 LogNa 0.133 0.874 0.065 -0.211 -0.115 0.844 LogK 0.387 0.849 -0.116 -0.130 -0.097 0.911 Ba 0.403 0.728 0.319 0.026 -0.060 0.799 Table 2.. Median values for the contents of acid-soluble elements in Li 0.601 0.715 -0.028 0.059 0.111 0.889 overbank sediments from the city of Trondheim and the Trøndelag LogSc 0.644 0.677 -0.173 -0.151 -0.098 0.936 region, Norway. LogB 0.096 0.567 0.134 0.289 -0.421 0.609 LogPb -0.067 -0.109 0.866 0.098 0.076 0.781 LogZn 0.183 0.018 0.822 -0.086 -0.304 0.809 Element Surface soil, Overbank sediments Overbank sediments LogCd 0.057 -0.038 0.736 0.007 -0.321 0.650 (mg/kg) Trondheim Trøndelag region Nidelva river.Trondheim LogHg -0.178 -0.183 0.607 0.366 0.310 0.664 (N=314) (N=55) (N=25) LogpH -0.213 0.086 0.578 0.478 -0.124 0.630 Al 18 600 17 400 10 000 LogAs 0.055 0.189 0.394 0.127 -0.327 0.317 As 2.8 2.8 < 3 LogLOI 0.051 -0.046 0.112 0.853 -0.048 0.747 B5.04.1< 3 LogS -0.105 -0.154 0.200 0.809 -0.354 0.854 Ba 72.2 43 46.8 LogSe 0.260 -0.153 -0.026 0.743 -0.060 0.648 Ca 5 400 5 000 2 700 LogCa 0.074 0.114 0.090 0.164 -0.906 0.873 Co 13.5 15.7 8.5 LogCu 0.351 0.075 0.384 0.074 -0.640 0.691 Cu 34.5 27 28.9 LogSr 0.072 0.481 0.217 0.322 -0.529 0.667 Cr 69.3 53.6 43.4 Fe 31 000 25 000 17 000 Variance 8.7716 6.0103 3.3380 2.7822 2.4769 23.3789 K 2 300 1 500 2 500 % Var 0.302 0.207 0.115 0.096 0.085 0.806 La 15.4 23 8.3 Li 17.8 13.3 5.2 Mg 12 900 9 200 7 100 Table 4. Minerals detected by X-ray diffraction (XRD) in surface soils Mn 442 400 136 from Trondheim, Norway. Na 20 30 40 Ni 45 35.6 32.9 Å 794 900 771 Mineral Characteristic chemical elements Pb 35 9.6 < 3 Amphibole Si, Al, Mg, Ca, Na, Ni, Co, Cr, Cu Sc 3.3 5.2 2.7 Chlorite Si, Mg, Fe, Al, Li, Mn, Ni, B Sr 27.0 28.1 17.5 Biotite Si Ti 1 110 1 200 850 Muscovite Si, Fe, Mg, Al, K V 55.1 40.4 30.5 Plagioclase Si,Al,Fe,Ca,Na,Ba Zn 98 44 37.9 Potassium feldspar Si, Al, K, Na, Ba 60363_NGUBull438_INNMAT 21.04.05 12:57 Side 66

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Fig. 3. Content of acid-soluble AS, Hg, Ni, and Pb (moving median) in surface soils from Trondheim. 60363_NGUBull438_INNMAT 21.04.05 12:57 Side 67

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Factor analysis of the dataset indicates certain element associations that point to particular sources. Factor 1 (Table 3) explains a significant part of the variance for Al, Co, Cr, Fe, Li, Mg, Mn, Ni, Sc, Ti and V in the surface soil. For these ele- ments, the communalities are relatively high ( >0.8). Factor 2 explains a significant part of the variance for Al, B, Ba, La, Li, Na, Sc and Y. Except for B, all the elements of fac- tor 2 have high communalities. The mineralogical analysis (Table 4) shows that natural minerals contribute to the Al, Ba,Ca,Cr,Fe,K,La,Li,Mg,Mn,Na,Ni,Sc,Si,Ti,and Y concentra- Fig. 4. Enrichment factors for As, Pb, Cd, Cu, Cr,, Hg, Ni and Zn in the area tions of the samples. Since these elements belong to factors close to the wasteincinerator (B - Fig. 1),Trondheim, Norway. 1 and 2, local geology probably controls the covariation between elements within these factors.As an example,it can be seen that the distribution of Ni in soil (Fig. 3) is largely related to occurrences of basic volcanic rocks in the Trondheim region (Gale & Roberts 1974,Wolff 1979). Factor 3 includes Pb, Zn, Cd, Hg and P.The communalities for Cd, Hg and P are relatively low, and only 65% of the vari- ance for these elements is explained by the factor model. However, Pb and Zn are clearly enriched in the surface soil compared with the natural background represented by the deeper parts of overbank sediment profiles (Tables 1 and 2). It is assumed that Pb, Zn, Cd and Hg mainly have anthro- Fig. 5. Enrichment factors for As, Pb, Cd, Cu, Cr,, Hg, Ni and Zn in the area pogenic sources. The highest concentrations of these ele- close to the crematorium and the hospital incinerator (B - Fig. 1), Trondheim, Norway. ments are found at some industrial sites and in the city cen- tre (Hg and Pb for example in Fig. 3).This pattern is common in several other cities around the world (Moir & Thornton tions for the whole dataset (Fig. 4). So far, the incinerator has 1989, Birke et al. 1992, Kelly et al. 1994, Viverette et al. 1996, not emitted sufficient quantities to pollute the nearby soil. Ottesen & Volden 1999). A large part of the variance for LOI, S and Se is explained Crematorium and hospital incinerator by factor 4. S and Se probably mainly reflect the content of In the area around the main crematorium and the hospital organic matter in the samples. Ca is described by factor 5. waste incinerator (marked B in Fig. 1) there is a clear Hg halo The model indicates a co-variance with Sr and Cu. in the downwind direction.The same area is also enriched in The variance of As is not explained by the factor model. Pb, Zn and Cd (Fig. 5). However, a main road passing through However, the geographical distribution of this element the area is also likely to influence the chemistry of the sur- shows that As concentrations are generally higher in the face soils. eastern part of Trondheim than in other parts of the city (Fig. 3). The eastern part of Trondheim has hosted several Crematorium and smelter industries burning coal such as a smelter,a rockwool factory, In the eastern part of the city, there is a crematorium, an and an abandoned gasworks. It is assumed that these are abandoned gasworks, and some heavy industry (marked C the probable sources of the elevated As concentrations. and D in Fig. 1). There is also a main road running through Evaluation of main pollution sources Municipal waste incinerator A municipal waste incinerator, located approximately 10 km south of the city centre, became operative in late 1985. The plant has two incinerators with a capacity of 13 tonnes waste /hour. The plant produces energy for central heating, covering 15 per cent of the heating requirements for the city. The flue gas passes through electrofilters for dust removal and then through a washing tower before being released from a 70 m-high chimney stack. Metal concentrations in samples collected within a Fig. 6. Enrichment factors for As, Pb, Cd, Cu, Cr,, Hg, Ni and Zn in the area radius of 2.5 km around the municipal waste incinerator close to the crematorium and heavy industry in the eastern part of the (marked A in Fig. 1) are lower than the median concentra- city of Trondheim. 60363_NGUBull438_INNMAT 21.04.05 12:57 Side 68

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Table 6.Contents of As and heavy metals in surface soils from Trondheim in relation to national acceptance levels.

Element Guidance level % of samples above guidance level As 2 mg/kg 83 % Pb 60 mg/kg 20 % Cd 3 mg/kg 0.3 % Cu 100 mg/kg 2.2 % Cr 25 mg/kg 96 % Hg 1 mg/kg 1.6 % Ni 50 mg/kg 40 % Fig. 7. Enrichment factors for As, Pb, Cd, Cu, Cr,, Hg, Ni and Zn in the area Zn 100 mg/kg 50 % close to the main roads,Trondheim, Norway.

the area. In this part of the city, the surface soils are enriched Large areas of Trondheim exceed these levels for As, Cr, Ni, in As, Pb, Cd, Hg and Zn (Fig.6). Pb and Zn (Table 6).Levels of Pb and Zn are mainly exceeded in the city centre, while concentrations of Cr, As and Ni Road traffic exceed the national guidelines throughout the study area. Samples collected close to the main roads are enriched in The guidelines consider all routes of exposure from soil to Pb, Hg, Zn and Cd (Fig.7).Leaded petrol is the most probable man. If the guidelines are exceeded, a specific risk analysis source for the Pb enrichment, while tyre wear may be the should be performed on the site. main source for Zn and Cd in these samples (Table 5). Elevated Pb levels were measured in the urban air compared Conclusions and practical Table 5. Contents of Zn and Cd in tyres (Duun-Moen 1996). implications Local geology and rock types account for the fundamental, Tyre Zn (mg/kg) Cd mg/kg background compositions of urban soils in Trondheim, cen- Sample 1 17 450 0.4 tral Norway. However, concentrations of As, Cd, Hg, Pb and Sample 2 19 350 5.9 Zn are influenced by pollution sources such as road traffic, Sample 3 14 050 1.9 local industry, crematoria and a hospital waste incinerator. Sample 4 15 050 0.7 Concentrations of As, Cr, Ni, Pb and Zn exceed the national guidance levels for sensitive land-use over large areas of the to rural air before the amount of lead in petrol was reduced city. The data indicate that there is a definite need for a (Hagen et al. 1989). health risk evaluation.

Ore mill Severe As and heavy metal pollution (Fig. 8) has been Acknowledgements reported from an abandoned ore mill in the western part of The authors wishes to thank Professors Bjørn Bølviken and Eiliv Steinnes the harbour. for their helpful discussions and thorough reviews, which helped to improve the paper. Assistance from the editor, Roberts, during final revisions of the manuscript are acknowledged with thanks. Results in relation to national guidance levels In Norway, the national guidance levels advise concentra- References tions that are generally safe for sensitive land-use such as Ahlgren, M. 1996: Undersökning I Falun av markblyets biotilgänglighet. children´s playgrounds and commercial market gardening. Universitet, Ekotoxikologiska avdelingen nr 42, 86 pp. Berglund, M., Fahlgren, L., Freland, M. & Vahter, M. 1994: Metaller i mark i innerstad och kranskommuner – förekomst och häl- sorisker för barn. Institutet för miljömedisin, Karoliska Institutet I samarbete med Miljöförvaltningen i stad, IMM-rapport 2/94. 46 pp. Birke, M., Rauch, U. & Helmert, M. 1992: Umweltgeokemie des Ballungsraumes Berlin -Schõneide: teil 1: Bearbeitungsmetodik - Elementverteilung in Bõden und Grundwassern. Zeitschrift für angewandte geologie, 38, 37 - 66. Birke, M. & Rauch, U. 1994: Geochemical investigation of the urban area of Berlin. Federal Institute of Geosciences and Natural Resources, Branch Office Berlin, Germany, 13 pp. Chen, T.B., Wong, J.W.C., Zhou, H.Y. & Wong, M.H. 1997: Assessment of trace metal distribution and contamination in surface soils of Hong Fig. 8. Enrichment factors for As, Pb, Cd, Cu, Cr,, Hg, Ni and Zn at an aban- Kong. Environmental Pollution 96, 61-68. doned industrial site,Trondheim, Norway. 60363_NGUBull438_INNMAT 21.04.05 12:57 Side 69

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